328 NOISE

Why is it that cars often have problems after it hat a service in a F shop ? So many times I read this in the threads and I have personaly bad experiences. Is there something wrong with the mechanics working on those cars ?

 

Does your car have the check valves that introduce fresh air into the exhaust stream during cat warmup (one on each bank)? When mine rust out vehicle makes a gurgling sound - 1987 GTS.
If that happens to be the problem, GM check valves fit.

 

Are all the plug wires fully seated?

 

Another possibility is the individual exhaust 'sampling' tubes attached to the exhaust header. They eventually rust out where they screw into the headers. Mine did that on the front bank (of course because the fix requires a lot more effort to remedy).

 

I'll tell you why.

The car is now close to 40 years old. Many exhaust components that are made of steel are now rusted and corroded to the point of breaking off causing an exhaust leak. The components can barely seal against leak if you leave them alone but as soon as they are touched, disturbed, or moved, they break and leak air. The components are packed into the engine bay so tight that in order to change one thing, you have to move a bunch of things to get to the one thing you need to change. So, in this case, the exhaust leak (the pulsing of the noise indicates an exhaust leak) can be caused by:

1) the rusted T-connection at the pulsed air injection
2) the rusted header connection to the pulse air injection
3) the rusted out exhaust air sampling ports

All of these rusted components are not caused by the mechanic, rather it's old age of the components.

While rule number 1 in auto-mechanic is "if something breaks right after the mechanic has fixed the car, it is something he/she did." With a 40 years old car, there is an additional explanation. Old age of components.

 

Lawrence hypothesis would make sense only if your car has a catalytic converter...but please be remembered that all "Euro" 328s (= all continental Europe, and UK RHDs, EXCEPT Swiss/Sweden variant after 1987) DO NOT HAVE CATS, nor therefore do they have tubes to introduce fresh air in the exhaust stream...
If your car is an "Euro", then it could not be this...

Does the car revs normally above 3.000 rpm?
If it does not, might be:
- an exhaust leak; if serious, such as a broken manifold at the outlet of one cylinder, then the car would not deliver much power after 3.000 rpm, and the engine would make a noise akin to an harvester (ask me how I know...)
- a disconected plug wire, meaning the car runs only on seven cylinders; if this would be the case, then the engine noise would not be "full", and the engine would vibrate abnormally.

Rgds

 

Lawrence,

See my post above; I seem to recall that his car is an "Euro", which do not have a catalytic converter, nor the "dilution tubes" attached to the headers...no emission control device whatsoever, and plain manifolds, not "wrapped".

Rgds

 

I had a similar issue on my 86 US spec GTS about a year ago. Turned out to be a plug issue, similar to what @nerofer mentions above. I didn't diagnose it myself, but my local mechanic found it and fixed it quickly.

 

Well, as always: there are two sides to that coin.

The good side is that it is nothing serious, but a very common obsolescence problem; and furthermore, it happens to the rear bank manifold, which is the easiest one to access. So sleep well my friend, your car is still healthy and it should be rather easy to fix.

The "not so good" side (actually, there is not really any bad side here) is that it usually can be repaired by welding a gusset or even a sleeve above it, but, while it is certainly not that difficult, it should be done by someone who knows how to weld exhaust tubes, and it also depends on how much/how bad of the tube is broken.

Actually, this would be my prefered option - and the one I choose when I had a similar problem, so here I have practised what I preach.
(but others might disagree, and I won't be hurt if they do).
To me (to me...but as said by the french humorist Pierre Dac so many years ago "this is my advice, and I share it myself") it would make no sense to have one brand new manifold at the rear, and an old one at the front waiting to crack.
Should you decide to change one, honestly my advice would be to change both, so the engine, manifold-wise, would be "zero timed"...
Trouble here is that it is much more difficult to change the front one. It can be done without pulling the engine out...just, but you need someone with very small hands.

There is the cost matter also. New OEM manifolds are expensive, and the OEM manifolds are very heavy: I have a reserve OEM set on a shelf in the garage, and they are VERY heavy.
So...should money be not much of a problem, I would suggest going "the whole hog", and change for a top-category aftermarket parts such as Tubi, or Larini , or anything equivalent; manifolds, intermediary pipes, and muffler. Lighter, shinier, better sounding.

That's what I'm planning to do in the near future; and having the engine to do this, so "while we are at it", lots of other things might be surveyed. Engine mounts changed, suspension worked on, etc, etc...the sky (and money) is the limit.

So you have different options here...and you can mitigate your cost(s).

Rgds

 

I had a similar problem after getting my 328 back from a service at the dealer. Rough running, sputtering, seemed like no power. It turned out to be a relay on the ECU board. It was diagnosed by my Porsche mechanic, as it was a Saturday and he was doing me a favor. Sorry I don’t know the part number but it was about an inch square and two inches long and had a fuse on it. My mechanic plugged in a Porsche equivalent he happened to have in his tool box and it solved the problem. The Porsche part had no fuse on it but it solved the problem and I replaced it with the correct fused version next chance I got. It was only about a $125 part at the time.

 

The mention of Sicily in the original post did not register with me. Well, at least I was talking about exhaust leakage.

 

Sicily means you are in Italy. The rear exhaust manifold is the first to fail: do not weld it, buy a new one.
Here in Italy Ferrari service is not bad at all and 35 years are enough for the rear exhaust manifold: it failed by itself.

Ciao

 

Two of my grandparents were born in Sicily. Other side was born in Naples. Been there.

Ciao

 

Vince:

Your problem sounds like it was a bad Frequency Valve Protection Relay…a very common problem. And, yes, some Porsches use the same $125 part (readily available at Pelican Parts). Sure way to diagnose this is to touch the blue Frequency Valve to see if it’s buzzing (as it should be). If it’s not, and the car is running rough, the FVPR is usually the culprit.

Alan
N.J.